Why not use hydrogen, its cheap and zeppelins can be smaller and fly higher.
We will maybe better in avoiding accidents compared to 1937:
- have better materials
- can use it only for cargo with drones - no human should travel with them!
- should/can use routes to avoid cities, and should/could build some separate safe landing space
etc...
finally:
Hydrogen fires are less destructive to immediate surroundings than gasoline explosions because of the buoyancy of H2, which causes heat of combustion to be released upwards more than circumferentially as the leaked mass ascends in the atmosphere; hydrogen fires are more survivable than fires of gasoline or wood.[22] The hydrogen in the Hindenburg burned out within about 90 seconds